U.S. patent number 4,829,226 [Application Number 07/207,828] was granted by the patent office on 1989-05-09 for rechargeable battery pack and charger unit combination.
This patent grant is currently assigned to Matsushita Electric Works, Ltd.. Invention is credited to Kouichi Iwanaga, Masami Kitamura, Katsuji Nakamura.
United States Patent |
4,829,226 |
Nakamura , et al. |
May 9, 1989 |
Rechargeable battery pack and charger unit combination
Abstract
A battery pack containing a rechargeable battery is detachable
to a charger unit for charging under the control of a charging
circuit in the charger unit. The battery pack includes a sensor
output circuit which comprises a temperature sensor for sensing the
temperature of the battery being charged. A voltage dividing
resistor network is formed in the sensor output circuit and
receives a constant current from the charging circuit upon
attachment of the battery pack to the charger unit such that it
provides an enable signal of a first voltage level to the charging
circuit for allowing the charging of the battery at a first charge
rate so long as the sensed battery temperature is below a
predetermined reference level. When the sensed battery temperature
exceeds the reference level, the voltage dividing resistor network
responds to provide a stop signal of a second voltage level for
inhibiting the charging at the first charge rate. Also included in
the sensor output circuit is a hold circuit which holds to provide
the stop signal to the charging circuit once the sensed temperature
exceeds the reference level.
Inventors: |
Nakamura; Katsuji (Hikone,
JP), Kitamura; Masami (Kanzaki, JP),
Iwanaga; Kouichi (Hikone, JP) |
Assignee: |
Matsushita Electric Works, Ltd.
(Kadoma, JP)
|
Family
ID: |
15572561 |
Appl.
No.: |
07/207,828 |
Filed: |
June 17, 1988 |
Foreign Application Priority Data
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|
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Sep 16, 1987 [JP] |
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62-153900 |
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Current U.S.
Class: |
320/112; 320/150;
D13/107 |
Current CPC
Class: |
H02J
7/0042 (20130101); H02J 7/0091 (20130101) |
Current International
Class: |
H02J
7/00 (20060101); H02J 007/04 (); H01M 010/44 () |
Field of
Search: |
;320/2,35,36 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hickey; R. J.
Attorney, Agent or Firm: Armstrong, Nikaido, Marmelstein,
Kubovcik & Murray
Claims
What is claimed is:
1. A combination comprising a battery pack accommodating therein a
rechargeable battery and a charger unit detachably receiving said
battery pack,
said charger unit including a charging circuit for charging said
rechargeable battery, said battery pack including a sensor output
circuit which comprises temperature sensor means for sensing the
temperature of said rechargeable battery being charged, said sensor
output circuit being cooperative with said temperature sensor means
to provide an enable signal of a first voltage level to said
charging circuit for allowing the charging of said rechargeable
battery at a first charge rate when the sensed battery temperature
is below a predetermined reference level and to provide a stop
signal of a second voltage level to said charging circuit for
inhibiting said charging at the first charge rate when the sensed
battery temperature exceeds said reference level; said sensor
output circuit further including hold means which holds the sensor
output circuit to provide said stop signal to said charging circuit
once the sensed battery temperature exceeds said reference level;
and said battery pack having a pair of charge terminals and a
control terminal which come into electrical connection with said
charging circuit through respective contacts provided at said
charger unit when said battery pack is attached to said charger
unit, said pair of charge terminals passing therethrough a charge
current from said charging circuit to said rechargeable battery,
and said control terminal being cooperative with one of said charge
terminals to feed said enable and stop signals from said sensor
output circuit to said charging circuit.
2. A combination comprising a battery pack accommodating therein a
rechargeable battery and a charger unit detachably receiving said
battery pack,
said charger unit including a charging circuit for charging said
rechargeable battery, said battery pack including a sensor output
circuit which comprises temperature sensor means for sensing the
temperature of said rechargeable battery being charged and a
voltage dividing resistor network connected to receive a constant
current from said charging circuit, said voltage dividing resistor
network being cooperative with the temperature sensor means to
provide an enable signal of a first voltage level to said charging
circuit for allowing the charging of said rechargeable battery at a
first charge rate when the sensed battery temperature is below a
predetermined reference level and to provide a stop signal of a
second voltage level to said charging circuit for inhibiting said
charging at the first charge rate when the sensed battery
temperature exceeds said reference level; said sensor output
circuit further including hold means which holds the sensor output
circuit to provide said stop signal to said charging circuit once
the sensed battery temperature exceeds said reference level; and
said battery pack having a pair of charge terminals and a control
terminal which come into electrical connection with said charging
circuit through respective contacts provided at said charger unit
when said battery pack is attached to said charger unit, said pair
of charge terminals passing therethrough a charge current from said
charging circuit to said rechargeable battery, and said control
terminal being cooperative with one of said charge terminals to
feed said enable and stop signals from said sensor output circuit
to said charging circuit.
3. A combination as set forth in claim 2, wherein said temperature
sensor is a thermoswitch which is closed when the sensed battery
temperature is below said reference level and is opened when the
sensed temperature exceeds said reference level, and wherein said
sensor output circuit comprises a series combination of a first
resistor, a second resistor and said thermoswitch connected across
said control terminal and said one of the charge terminals, a pair
of first and second transistors with their respective emitter-base
paths connected in series circuit in parallel relation to the
series combination of said second resistor and said thermoswitch,
and a third resistor connected in series relation with said
thermoswitch between the base-emitter path of said second
transistor; whereby said pair of first and second transistor define
said holding means and said first and second resistors define said
voltage dividing resistor network.
4. A combination as set forth in claim 3, wherein said rechargeable
battery is composed of three or more cylindrical cells at least
three of which are packed together in parallel relation with their
longitudinal axis in parallel relation to each other so as to leave
between the adjacent rounded side surfaces a confined space for
receiving therein said thermoswitch.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a rechargeable battery pack
and charger unit combination.
2. Background Art
Such combination of a rechargeable battery pack and a charger unit
has been widely utilized for power driven devices such as
screwdrivers or the like portable tools. The charger unit includes
a charging circuit which is controlled to supply a charge current
to the rechargeable battery in the battery pack until the battery
is fully charged. For a certain type of the rechargeable battery,
it has been a practice to monitor the temperature of the battery
being charged as an effective parameter indicating the terminal
voltage of the battery in order to control the charging circuit. To
this end, a temperature sensor is included in the battery pack for
transmitting a sensor output indicative of the battery temperature,
or the charge condition of the battery to the charging circuit for
control thereof. As disclosed in the Japanese Utility Model
Publication (KOKAI) No. 56-48241 published on Apr. 28, 1981, a
prior charge control scheme based upon the battery temperature
requires in the charger circuit a judge-and-hold circuit which
judges from the output of the temperature sensor that the battery
temperature or the terminal voltage exceeds a predetermined
critical level to be indicative of the battery being fully charged,
and which holds the charger circuit in an OFF condition of
supplying no charging current to the battery once the fully charged
condition is judged for prevention of the overcharging which would
otherwise result as the battery temperature falls below the
critical reference level.
In the meanwhile, there have been proposed in the art a wide
variety of battery packs with rechargeable batteries of different
voltage-temperature characteristics. In this connection, it is
required to use different temperature sensors particularly
compatible with the kinds of the rechargeable batteries selected
for providing a reliable sensor output well indicative of the fully
charged condition of the rechargeable battery. This means that the
temperature sensors with the outputs of differing levels are used
within the battery packs of different types. If this is the case,
the charger unit is also required to incorporate the judge-and-hold
circuit which is particularly designed in exact correspondence with
the output level of the sensor selected in the particular battery
pack. With this result, different types of the charger units may be
required for different types of the battery packs. This is not
economical in view of that different types of battery packs may be
required for different power operated devices but a single type of
the charger unit is enough for charging. Therefore, it is highly
desired to utilize the battery charger common to the different
types of the battery packs utilizing different temperature
sensors.
SUMMARY OF THE INVENTION
The above problem has been eliminated in the present invention
which utilizes a battery pack capable of providing outputs of
different adjustable voltage levels in response to the sensed
battery temperature. In the battery pack and charger unit
combination in accordance with the present invention, the battery
pack accommodating a rechargeable battery is detachable to the
charger unit including a charging circuit for charging the
rechargeable battery. Included in the battery pack is a sensor
output circuit which comprises temperature sensor means for sensing
the battery temperature and a voltage dividing resistor network
connected to receive a constant current from said charging circuit.
The voltage dividing resistor network is cooperative with the
temperature sensor means to provide an enable signal of a first
voltage level to the charging circuit for allowing the charging of
the rechargeable battery at a first charge rate when the sensed
battery temperature is below a predetermined reference level and to
provide a stop signal of a second voltage level to the charging
circuit for inhibiting the charging at the first charge rate when
the sensed battery temperature exceeds said reference level. Also
included in the sensor output circuit is a hold circuit which holds
the voltage dividing network to provide the stop signal once the
battery temperature exceeds the reference voltage for preventing
the battery from being overcharged. Thus, the battery pack can
provide the enable and stop signals of which voltage levels can be
adjusted through the voltage dividing resistor network to desired
levels acceptable by the charging circuit in the charger unit for
control of the charging circuit. With this result, it is possible
to use the charging circuit or the charger unit common to differing
types of the battery packs utilizing particular temperature sensors
having different sensor output levels for indication of the fully
charged condition.
Accordingly, it is a primary object of the present invention to
provide a battery pack and charger unit combination which allows
the use of the charger unit common to the different types of the
battery packs, while effecting controlled charging based upon the
battery temperature.
The battery pack is provided with a pair of charge terminals and a
control terminal which come into electrical connection with the
charging circuit through respective contacts provided at said
charger unit when said battery pack is attached to said charger
unit. The pair of charge terminals is used for passing therethrough
a charge current from the charging circuit to the rechargeable
battery, while the control terminal is cooperative with one of the
charge terminals to feed the enable and stop signals from the
sensor output circuit to the charging circuit. In a preferred
embodiment, the temperature sensor is a thermoswitch which is kept
closed so long as the sensed battery temperature is below the
predetermined reference level and is caused to open when the sensed
temperature exceeds the reference temperature level. The
thermoswitch is inserted in the sensor output circuit in series
connection with a first resistor and a second resistor. The series
combination of the thermoswitch, the first and second resistors is
connected across the control terminal and the one of the charge
terminals. Also included in the sensor output circuit is a pair of
first and second transistors having their respective emitter-base
paths connected in series circuit in parallel relation to the
series combination of the thermoswitch and the second resistors. A
third resistor is connected in series relation with the
thermoswitch between the base-emitter path of the second
transistor. The pair of first and second transistors define the
holding means and the first and second resistors define the voltage
dividing resistor network. With this circuit configuration, when
the thermoswitch is kept closed as a result of the battery
temperature remains below the reference level, the constant current
fed from the charging circuit flows through the first and second
resistors to provide the enable signal of the first voltage as a
function of the total resistance of the first and second resistors.
When the thermoswitch is opened in response to the battery
temperature exceeding the reference level, the second transistor is
biased through the third resistor to become conductive which in
turn makes the first transistor conductive for passing the constant
current through the base-emitter paths of the first and second
transistors so as to provide the stop signal of the second voltage
as a function of substantially only the first resistor. Therefore,
the first and second voltage can be adjusted to desired levels by
suitably selecting the first and second resistors, which is another
object of the present invention.
The rechargeable battery is preferably composed of a plurality of
cylindrical cells at least three of which are packed together in
parallel relation so as to leave between the adjacent rounded side
surfaces a space for receiving therein the thermoswitch. Thus, the
thermoswitch can be held in close proximity to each cell for
obtaining enhanced sensitivity while effectively utilizing the
space inherently formed between the cells for accommodating the
thermoswitch.
It is therefore a further object of the present invention to
provide a battery pack and charger combination in which the
temperature sensor can be located within the battery back at a
position effective for reliable battery temperature sensing and
space utilization.
These and the other objects and advantages of the present invention
will become more apparent from the following description of the
preferred embodiment of the present invention when taken in
conjunction with the accompany drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a battery pack and a charger unit,
shown in a connected position, in accordance with a preferred
embodiment of the present invention;
FIG. 2 is a sectional view of the charger unit taken along line
2--2 of FIG. 1 with the battery pack shown partly in section;
FIG. 3 is a perspective view of the battery pack;
FIG. 4 is a perspective view of a rechargeable battery accommodated
in the battery pack;
FIG. 5 is a schematic view of the cell arrangement of the
rechargeable battery within the battery pack;
FIG. 6 is a block diagram showing the circuit of a charging circuit
of the charger unit; and
FIG. 7 is a circuit diagram of a sensor output circuit included in
the battery pack.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1 to 3, there is shown a combination battery
pack and charger unit in accordance with a preferred embodiment of
the present invention. The battery pack 10 accommodates a
rechargeable battery 11 and is adapted in use to be inserted in a
power operated electrical device such as a portable screwdriver or
the like power tools for energizing the device. The battery pack 10
is provided at its one end with a pair of charge terminals 12 and
13 through which a current is supplied to the device. When
recharging is necessary, one end of the battery pack 10 is inserted
in a slot 21 of the charger unit 20 for connection of the
rechargeable battery 11 with a charging circuit 30 formed in the
charger unit 20. The battery pack 10 is also formed with a control
terminal 14 for providing to the charging circuit 30 a signal
indicative of the battery temperature which is in turn indicative
of the terminal voltage of the battery 11 being charged. These
terminals 12 to 14 are respectively engaged with corresponding
contacts 22 at the bottom of the slot 21 of the charger unit 20 for
connection with the charging circuit 30.
The charging circuit 30 comprises, as shown in FIG. 6, a rectifier
31, a switching element 32, and a control section 33. The rectifier
31, which is connected to a source of a.c. voltage, includes a
step-down transformer 34 (only seen in FIG. 2) to provide a charge
current to the rechargeable battery 11 by way of the switching
element 32. The control section 33 receives from the battery pack
10 the signal indicative of the battery temperature so as to
thereby control the switching element 32 in such a manner as to
effect the charging at a fist charge rate (i.e., supply a larger
charging current) and effect the charging at the second rate (i.e.,
supply a minute charge current or no current), selectively
depending upon the level of the battery temperature. After the
first rate charging is completed, the control section 33 causes an
indicator lamp 23 (seen in FIGS. 1 and 2) to turn on for indication
that the battery is fully charged.
The battery pack 10 includes a temperature sensor 15 which senses
the temperature of the rechargeable battery being charged as
indicative of the battery condition. In the present embodiment, a
thermoswitch TH is employed as the temperature sensor which has its
contact opened when the battery temperature is sensed to exceed a
predetermined reference level which is indicative of the battery
being fully charged. The thermoswitch TH has its contact kept
closed so long as the battery temperature is below the reference
temperature level. The rechargeable battery 11 is composed of eight
cylindrical cells 16 disposed within the battery pack 10 in a
manner as shown in FIG. 4. The bottom five cells 16 are closely
packed in parallel relation as shown in FIG. 5 so as to leave
between the four adjacent cells 16 a confined space S for receiving
the temperature sensor 15 or thermoswitch TH. Thus, the
thermoswitch TH can be held in close proximity to the cells for
ensuring improved sensitivity against the battery temperature while
effectively utilizing the space inherently formed between the
adjacent cells 16. Such confined space is always formed between at
least three cells when packed in parallel relation to each
other.
Also provided in the battery pack 10 is a sensor output circuit 18
which is connected between the control terminal 14 and the negative
charge terminal 13, as shown in FIG. 7. The sensor output circuit
18, which receives a constant current from the charging circuit 30
when the battery pack 10 is inserted in the charger unit 20,
comprises in addition to the thermoswitch TH, a voltage dividing
resistor network of a first resistor R.sub.1 and a second resistor
R.sub.2 ; and a hold circuit of a first transistor Q.sub.1 and a
second transistor Q.sub.2. The first and second resistor R.sub.1
and R.sub.2 are connected in series relation with the thermoswitch
TH between the control terminal 14 and the negative terminal 13.
The first and second transistors Q.sub.1 and Q.sub.2 have their
respective base-emitter paths connected in series in a parallel
relation to the series combination of the second resistor R.sub.2
and the thermoswitch TH. A third resistor R.sub.3 is connected in
series with the thermoswitch TH between the base-emitter path of
the second transistor Q2. A capacitor C is also connected in
parallel relation with the series combination of the second
resistor R.sub.2 and the thermoswitch TH for eliminating possible
noises which may result from the chattering of the thermoswitch TH.
In operation, so long as the thermoswitch TH is kept closed in
response to the battery temperature being below the reference
level, or the battery is not yet fully charged, the constant
current I from the charging circuit 30 will flow through the first
resistor R.sub.1, the second resistor R.sub.2, and the closed
thermoswitch TH to shunt the base-emitter path of the transistor
Q.sub.2, thereby keeping the second transistor Q.sub.2 and
therefore the first transistor Q.sub.1 nonconductive. Whereby there
is developed across the control terminal 14 and the negative charge
terminal 13 a voltage V.sub.81 [=I.times.(R.sub.1 +R.sub.2)], which
is fed to the control section 33 of the charging circuit 30 as an
enable signal for effecting the charging of the battery 11 at the
first charge rate. When the thermoswitch TH is caused to be opened
in response to the battery temperature exceeding the reference
level, the current I will flow through the first, second and third
resistors R1, R2, and R3 to bias the second transistor Q.sub.2
conductive, which in turn biases the third transistor Q.sub.3
conductive. Thus, the constant current I from the charging circuit
30 will flow through the first resistor R.sub.1, the first
transistor Q.sub.1, and the second transistor Q.sub.2 to develop
across the control terminal 14 and the negative charge terminal 13
a voltage V.sub.82 [=I.R.sub.3 +V.sub.BE, wherein V.sub.BE is the
base-emitter voltage of the first and second transistors Q.sub.1
and Q.sub.2 ], which is fed to the control section 33 of the
charging circuit 30 as a stop signal for inhibiting the charging at
the first rate or stopping the charge. Once the transistors Q.sub.1
and Q.sub.2 become conductive, they are latched in the conductive
condition to hold the circuit to provide the stop signal even when
the thermoswitch TH is again closed in response to the battery
temperature falling below the reference level, preventing the
overcharging of the battery. With the provision of the voltage
dividing network in the sensor output circuit 18, the enable and
stop signals developed across the control terminal 14 and the
negative charge terminal 13 can be of any voltage level that
matches with the requirement of the control section 33 of the
charging circuit 30 by suitably selecting the values of the first
and second resistors R.sub.1 and R.sub.2. Consequently, different
types of battery packs, which utilize temperature sensors having
the characteristics of producing differing output levels for
indication of the battery condition, can be adjusted to provide the
enable and stop signals of the same voltage level common to and
therefore acceptable to a single type of the charger unit or the
control section 33 of the charging circuit 30 therein. Such
differing temperature sensors include, for example, a diode,
thermistor, and posistor. The latching condition of the transistors
Q.sub.1 and Q.sub.2 are reset when the battery pack 10 is detached
from the charger unit 10 to disconnect the sensor output circuit 18
from the charging circuit 30. Although the thermoswitch TH is
utilized as the temperature sensor in the above embodiment, it is
equally possible to use the diode, thermistor, and posistor as the
temperature sensor with suitable modification of the circuit.
* * * * *